giraph-core/src/main/java/org/apache/giraph/utils/EmptyIterable.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.giraph.utils;

import java.util.Collections;

import java.util.Iterator;

/**
 * Singleton class for empty iterables.
 *
 * @param <T> Element type
 */
public class EmptyIterable<T> implements Iterable<T> {
  /** Singleton empty iterable */
  private static final EmptyIterable EMPTY_ITERABLE = new EmptyIterable();

  /**
   * Get the singleton empty iterable
   *
   * @param <T> Element type
   * @return Singleton empty iterable
   */
  public static <T> Iterable<T> get() {
    return (Iterable<T>) EMPTY_ITERABLE;
  }

  @Override
  public Iterator<T> iterator() {
    return Collections.emptyIterator();
  }
}